Catalytic domain of the Protein Serine/Threonine Kinase, Protein Kinase B gamma. Serine/Threonine Kinases (STKs), Protein Kinase B (PKB) or Akt subfamily, gamma (or Akt3) isoform, catalytic (c) domain. STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. The PKB subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. There are three PKB isoforms from different genes, PKB-alpha (or Akt1), PKB-beta (or Akt2), and PKB-gamma (or Akt3). PKB contains an N-terminal pleckstrin homology (PH) domain and a C-terminal catalytic domain. PKB-gamma is predominantly expressed in neuronal tissues. Mice deficient in PKB-gamma show a reduction in brain weight due to the decreases in cell size and cell number. PKB-gamma has also been shown to be upregulated in estrogen-deficient breast cancer cells, androgen-independent prostate cancer cells, and primary ovarian tumors. It acts as a key mediator in the genesis of ovarian cancer.